<template>
  <div> 
    <h1>当前求和为:{{total}}</h1>
    <select v-model.number="n">
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
    </select>
    <button @click="increment">+</button>
    <button @click="decrement">-</button>
    <button @click="incrementOdd">当前求和为奇数再加</button>
    <button @click="incrementWait">等一等再加</button>
  </div>
</template>

<script>
  export default {
    name:'Count', 
    data(){
      return { 
        n:1, // 用户选择的数据
        total: 0 // 总和 
      }
    },
    methods: {
      increment(){
        this.total += this.n
      },
      decrement(){
        this.total -= this.n
      },
      incrementOdd(){
        if(this.total % 2){
          this.total += this.n
        }
      },
      incrementWait(){
        setTimeout(() => {
          this.total += this.n
        }, 500)
      }
    },
  }
</script>
<style>
  button{
    margin-left: 10px;
  }
</style>